TestA.as
package {
import flash.display.Sprite;
public class TestA extends Sprite{
  public function TestA(){
   var testB:TestB = new TestB();		
  }
 }
}

TestB.as
package{
 public class TestB{
  public function TestB(){}
 }
}

[Compiler] Error #1046: Type was not found or was not a compile-time constant: TestB.
　var testb:TestB = new TestB();
ReferenceError: Error #1065: 変数 TestA は定義されていません。